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Photochemical smog 6.3 - Coggle Diagram
Photochemical smog 6.3
Primary pollutants
Carbon monoxide and CO2
: colourless, odorless and greenhouse gases
Can be natural or anthropogenic - emitted directly from the pollution source
Soot, unburnt hydrocarbons:
Solid particles suspended in the air = formed from combustion of fossil fuels, can produce smog + contribute to cancer, heart disease, cancers.
Oxides of N:
when N and O come together under high temps. Occurs in hot exhaust gas from vehicles, factories...
Odies of S
: from combustion of S containing fuels - oil, coal.... From power plants, petrol refineries.
Factors
Topography
: Urban climates affects the formation of O3. Urban areas have less vegetation and higher heat radiated from buildings.
Climate
: Accumulation is highest when there is more sunlight = more UV radiation
Population density
: The more cars = the higher the tropospheric ozone production
Secondary pollutants
Tropospheric ozone is secondary as it is formed from the interaction between NOx and other pollutants.
Tropospheric ozone
NO and hydrocarbons form from the combustion of fossil fuels in car emmissions.
NO reacts with O2 to form NO2 (gas contributing to urban haze). NO2 absorbs sunlight breaking into O atoms to bond with O2 to create tropospheric ozone.
Effects
Irritates eyes, damages crops and forests, impair an athlete's performance, create more frequent attacks for individuals with asthma, cause eye irritation, chest pain, coughing, nausea, headaches and chest congestion and discomfort.
High concentrations cause plants to close their stomata = cells under the plant allowing CO2 + H2O to diffuse into the plant tissue = slows down photosynthesis and growth.
Rubber, textile dyes, fibers, and certain paints may be weakened or damaged by exposure.
Sources:
Transport, cooking, heating, power generation
Ozone occurs naturally at ground-level in low concentrations. 2 sources = hydrocarbons, = released by plants + soil. And small amounts of stratospheric ozone who migrate to earth's surface. Neither contributes enough ozone to be a threat to health or the environment.
Thermal inversion
These trap the smog in valleys or basins e.g. Sao Paulo or LA
The warm air is unable to disperse as the cold air (denser) from surrounding mountains or hills disallows the warm air from rising. This means the smog is trapped.
The concentrations can build to harmful or even lethal levels and produce toxic and cancirogenic chemicals.
Deforestation and burning can also lead to smog as slash and burn is common. CO2 increases (due to release). eg Asian 'brown haze' 2012 -2014
Economic effects
Cost of cleanup strategies, tropism loss, increases healthcare costs, decreased worker productivity and crop productivity, cost of replacing materials.
World bank predicts the cost of air pollution for china is around 4% of its GDP
Winds disperse the smog and precipitation cleans the air
Pollution management
Alter human activity
Consume less, burn less fossil fuels
Use public transport, walking or cycling
Decrease consumption of non-essential goods
Promotion of clean tech / hybrid cars
Regulate
Use catalytic converters to reduce NOx
Only allow certain cars into a city on certain days (e.g. odd v even)
International agreements
Relocate industries from centre of population
Filter and catch pollutants at the point of emission
Clean up
Scrubbers
Reforestation
Conservation areas
Spray water at junctions to 'wash out' pollution from the atmosphere
But
Most urban pollution comes from old cars
Public transport can be expensive / inconvenient
Catalytic converters increase CO2 emissions + can reduce fuel efficiency
Key aspects
The combustion of fossil fuels may lead to the formation of primary pollutants leading to secondary pollutants and perhaps smog. The smog is a combination of 100+ primary and secondary pollutants formed under sunlight, ozone being the main one.
Fossil fuels are burned leading to the release of NOx in vehicle emissions. In the presence of sunlight = primary pollutants, these pollutants interact with other to produce secondary pollutants e.g. tropospheric ozone.
The tropospheric ozone formation takes time hence, this may have moved over other suburban areas or surrounding.